Hi @nuraqlima and @rfeigel , ok I’ve read and now re-read this and I think I understand now what is being asked.
Firstly, with the aid of OCR provided by chatGPT, I’v reproduced here the data from the screenshot. It might not be entirely accurate, but it’s good enough for our purposes:
| BOD (mg/L) | BOD INDEX | Ca (mg/L) | Cd (mg/L) | Cl (mg/L) | COD (mg/L) | COD INDEX | Cr (mg/L) | CN (mg/L) | E. coli (cfu/100ml) | Fe (mg/L) |
|---|---|---|---|---|---|---|---|---|---|---|
| 5 | 79 | 19.8 | <0.001 | 8 | 24 | 70 | <0.001 | <0.050 | 540,000 | 0.74 |
| 2 | 92 | 14.0 | <0.001 | 3 | 26 | 78 | <0.001 | <0.050 | 14,000 | 0.26 |
| 4 | 83 | 12.3 | <0.001 | 5 | 16 | 32 | <0.001 | <0.050 | 460,000 | 0.61 |
| 1 | 61 | 27.8 | <0.001 | 6 | 27 | 37 | <0.001 | <0.050 | 900,000 | 0.82 |
| 7 | 73 | 18.4 | <0.001 | 9 | 36 | 61 | <0.001 | <0.050 | 230,000 | 0.69 |
| 8 | 69 | 18.9 | <0.001 | 21 | 29 | 62 | <0.001 | <0.050 | 250,000 | 0.87 |
| 1 | 45 | 27.8 | <0.001 | 27 | 28 | 61 | <0.001 | <0.050 | 280,000 | 0.87 |
| 6 | 57 | 30.3 | <0.001 | 6 | 18 | 54 | <0.001 | <0.050 | 46,000 | 0.55 |
| 9 | 29 | 32.7 | <0.001 | 14 | 28 | 64 | <0.001 | <0.050 | 24,000 | 0.48 |
| 3 | 73 | 28.7 | <0.001 | 15 | 32 | 63 | <0.001 | <0.050 | 140,000 | 1.24 |
(@nuraqlima, this is what @rfeigel meant by actually sharing some data, so either upload a sample from Excel, or upload in text form so that it can be copied/pasted and people can then experiment with possible solutions without having to do all the prep work which takes time and effort
see also Easy creation of formatted "table" on forum posts on how to easily make use of text data posted as above)
So, the columns Cd (mg/L) , Cr (mg/L) and CN (mg/L) may contain a numeric value but they may also contain a literal value <n or >n. The problem faced is that for this reason, these columns are represented as strings and not numerics, and so cannot be directly used within Math Formula node, and require conversion first.
My take on this “conversion” is as follows, (except that I’m not entirely sure if I got the >n correct)
For each of those columns, derive a value as below
| where the cell contains | use the formula value to determine the value | notes |
|---|---|---|
| n | n | |
| <n | n / 2 | |
| >n | (n / 2) +1 | (is this correct, it wasn’t clear to me from the handwritten note) |
So for example
| cell value | formula | calculated value |
|---|---|---|
| 10 | 10 | |
| <10 | 10 / 2 | 5 |
| >10 | (10 / 2) +1 | 6 |
The calculated value could then be used in any subsequent calculations, but I believe that what is being asked, is how to convert the <n and >n values to actual numeric values based on the above.
@nuraqlima , please can you confirm understanding. I’m sure that we can then give you a variety of methods to achieve this.